Punching shear is the most common failure mechanism of slabs that are supported directly on columns. The slab–column connection is always vulnerable to critical punching shear; thus, it is necessary to investigate the effect of various parameters on the punching shear behavior of the flat slabs. This work presents an experimental study to evaluate the effect of the level of prestressing force and layout of the strands on the punching shear behavior of the slab–column connection in terms of the maximum load, deflection, stiffness, ductility, and the absorbed energy. Five square post-tension flat slabs (2000 mm × 2000 mm) with 150 mm thickness were tested. Increasing the prestressing force increased the maximum load and the ductility with a delay in damage in the case of uniformly distributed strands. Additionally, the banded layout of the post-tensioning strands significantly increased the punching shear capacity of the post-tensioned flat slabs at all levels of prestressing. The influence of the layout of the strands on the flat slab ductility is clearly visible in cases of high prestressing force as the ductility decreases in cases with distributed strands when compared to the same flat slabs with banded strands. Finally, the predicted values of the ultimate load of the punching shear using different codes, including the Egyptian Code of Practice (ECP-203), the American Building code (ACI-318), the CEB-FIP Model code and the Euro code, are compared to the experimental values of the ultimate punching shear strength of the post-tensioned and non-post-tensioned flat slabs.

Glass Fiber Reinforced Polymer (GFRP) is a promising alternative to steel due to its high strength, lightweight properties, corrosion resistance, and low maintenance requirements. This study examines the effect of internal GFRP I-sections on the axial load capacity and fire resistance of reinforced concrete (RC) columns. The experimental program consisted of two groups: the first group, conventional RC columns, with one exposed to 500°C for 90 minutes and the other unheated, and the second group, GFRP I-section reinforced columns, similarly tested under fire and control conditions. Results show that GFRP-reinforced columns exhibited a 17% higher axial capacity than conventional RC columns. However, fire exposure reduced the axial strength of GFRP-reinforced columns by 39% compared to unheated specimens and by 14% compared to conventional RC columns. Theoretical axial load capacities were calculated using design codes, and finite element analysis (FEA) validated the experimental results. Additional parameters, including concrete strength, steel yield strength, reinforcement ratio, and GFRP section properties, were analyzed. The strong correlation between experimental, theoretical, and numerical results provides a foundation for developing practical design guidelines for GFRP-reinforced composite columns.

Glass Fiber Reinforced Polymer (GFRP) I-sections offer a promising alternative to traditional steel reinforcement due to their reduced weight and maintenance requirements. This study aims to optimize the design of GFRP-reinforced composite concrete beams for cost-effective solutions. Twelve tested beams were tested under four-point bending loading, divided into four groups with varying depths: three conventional reinforced concrete (RC) beams as control specimens; nine beams with GFRP I-sections positioned internally; externally; and internally with exposure to 500°C for 90 minutes. The test results indicate that GFRP-reinforced beams exhibit superior strength and bending resistance compared to conventional RC beams where an increase in maximum load ranging from 62% to 113% and reduced deflection at the same load level. Optimal performance was observed when GFRP I-sections were placed near the tensioned fiber. Exposure to elevated temperatures resulted in minimal performance reductions, not exceeding 5% at yield load and 16% at maximum load comparing with composite tested specimens without exposure to elevated temperature. Theoretical analyses closely aligned with experimental results, providing a foundation for practical guidelines on the economical design of GFRP-reinforced composite.